Shahriar Wahid

Climate change and water resources in the Bagmati River Basin, Nepal

This paper characterizes potential hydrological impact of future climate in the Bagmati River Basin, Nepal. For this research, basinwide future hydrology is simulated by using downscaled temperature and precipitation outputs from the Hadley Centre Coupled Model, version 3 (HadCM3), and the Hydrologic Engineering Centers Hydrologic Modeling System (HEC-HMS). It is predicted that temperature may rise maximally during the summer rather than winter for both A2 and B2 Special Report on Emissions Scenarios (SRES) scenarios. Precipitation may increase during the wet season, but it may decrease during other seasons for A2 scenario. For B2 scenario, precipitation may increase during all the seasons. Under the A2 scenario, premonsoon water availability may decrease more in the upper than the middle basin. During monsoons, both upper and middle basins show increased water availability. During the postmonsoon season, water availability may decrease in the upper part, while the middle part shows a mixed trend. Under the B2 scenario, water availability is expected to increase in the entire basin. The analysis of the projected hydrologic impact of climate change is expected to support informed decision-making for sustainable water management.

Indicator-Based Approach for Assessing the Vulnerability of Freshwater Resources in the Bagmati River Basin, Nepal

To assess the vulnerability of water resources in the Bagmati River Basin in Nepal, this paper adopts an indicator-based approach wherein vulnerability is expressed as a function of water stress and adaptive capacity. Water stress encompasses indicators of water resources variation, scarcity, and exploitation and water pollution, whereas adaptive capacity covers indicators of natural, physical, human resource, and economic capacities. Based on the evaluation of eleven indicators, which were aggregated into eight vulnerability parameters, an increasingly stressful situation and lack of adaptive capacity became evident. Considerable spatial variation in indicator values suggests differential policy options. While the northern parts need attention to reduce pollution loading and conserve vegetation cover, the southern parts need improvements in physical capacity, i.e. water infrastructures. The comprehensive and easily interpretable findings of the study are expected to help decision makers reach sound solutions to reduce freshwater resources vulnerability in the Bagmati River Basin, Nepal. With its inherent flexibility, the approach has demonstrated its potential for application in different times and areas for monitoring and comparison purposes.

Estimation of Soil Erosion Dynamics in the Koshi Basin Using GIS and Remote Sensing to Assess Priority Areas for Conservation.

High levels of water-induced erosion in the transboundary Himalayan river basins are contributing to substantial changes in basin hydrology and inundation. Basin-wide information on erosion dynamics is needed for conservation planning, but field-based studies are limited. This study used remote sensing (RS) data and a geographic information system (GIS) to estimate the spatial distribution of soil erosion across the entire Koshi basin, to identify changes between 1990 and 2010, and to develop a conservation priority map. The revised universal soil loss equation (RUSLE) was used in an ArcGIS environment with rainfall erosivity, soil erodibility, slope length and steepness, cover-management, and support practice factors as primary parameters. The estimated annual erosion from the basin was around 40 million tonnes (40 million tonnes in 1990 and 42 million tonnes in 2010). The results were within the range of reported levels derived from isolated plot measurements and model estimates. Erosion risk was divided into eight classes from very low to extremely high and mapped to show the spatial pattern of soil erosion risk in the basin in 1990 and 2010. The erosion risk class remained unchanged between 1990 and 2010 in close to 87% of the study area, but increased over 9.0% of the area and decreased over 3.8%, indicating an overall worsening of the situation. Areas with a high and increasing risk of erosion were identified as priority areas for conservation. The study provides the first assessment of erosion dynamics at the basin level and provides a basis for identifying conservation priorities across the Koshi basin. The model has a good potential for application in similar river basins in the Himalayan region.

Spatial GR4J conceptualization of the Tamor glaciated alpine catchment in Eastern Nepal: evaluation of GR4JSG against streamflow and MODIS snow extent

Snow and glacial melt processes are an important part of the Himalayan water balance. Correct quantification of melt runoff processes is necessary to understand the regions vulnerability to climate change. This paper describes in detail an application of conceptual GR4J hydrological model in the Tamor catchment in Eastern Nepal using typical elevation band and degree-day factor approaches to model Himalayan snow and glacial melt processes. The model aims to provide a simple model that meets most water planning applications. The paper contributes a model conceptualization (GR4JSG) that enables coarse evaluation of modelled snow extents against remotely sensed Moderate Resolution Imaging Spectroradiometer snow extent. Novel aspects include the glacial store in GR4JSG and examination of how the parameters controlling snow and glacial stores correlate with existing parameters of GR4J. The model is calibrated using a Bayesian Monte Carlo Markov Chain method against observed streamflow for one glaciated catchment with reliable data. Evaluation of the modelled streamflow with observed streamflow gave Nash Sutcliffe Efficiency of 0.88 and Percent Bias of <4%. Comparison of the modelled snow extents with Moderate Resolution Imaging Spectroradiometer gave R2 of 0.46, with calibration against streamflow only. The contribution of melt runoff to total discharge from the catchment is 14–16% across different experiments. The model is highly sensitive to rainfall and temperature data, which suffer from known problems and biases, for example because of stations being located predominantly in valleys and at lower elevations. Testing of the model in other Himalayan catchments may reveal additional limitations.

Characteristics of landslide in Koshi River Basin, Central Himalaya

Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya (mostly small and medium size landslides in east-west direction) and the Transition Belt (mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfall-induced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum (Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations (2000~3000 m) and steeper slopes (40°~50°).

Designing community-based payment scheme for ecosystem services: a case from Koshi Hills, Nepal

The study was carried out to design payment for ecosystem services (PES) scheme to enhance the effectiveness of existing drinking water supply project. This study determined willingness-to-pay of water users using choice experiment method and identify the willingness of watershed households to participate in the scheme by household survey. The results suggest that creating a multi-stakeholder institution at the local level, led by local body, will make the implementation of the PES feasible. This would create trust between ecosystem managers and service consumers, facilitates monitoring system and encourages their participation in watershed management. In the beginning, water users would like to pay less than their willingness-to-pay because it may take time to improve the situation. This suggests that community-based payment for ecosystem services scheme in rural area can be kicked off, only after the external support this is because the amount committed by water users are not sufficient to implement all required activities and ecosystem managers will not make an investment expecting that they will be paid in the future. The study also recommends providing upstream communities in-kind support rather than cash may reduce the transportation cost as well as risk of corruption. This also ensures that the fund is spent on planned activities.

Agriculture under changing climate conditions and adaptation options in the Koshi Basin

Using biophysical and social analysis methods, this paper evaluated agricultural practices under changing climate in the Koshi Basin and assessed adaptation options. Agricultural trend analysis showed that in the recent three to four decades, the total cultivated area had declined in all parts of the basin except in the Nepal Mountain Region. Household survey results also confirmed such decline and further revealed shifts towards non-agricultural activities. Climate trend analysis showed changes in the frequency of wet and dry days in study districts, implying an increasing chance of flood and drought events. Household surveys further revealed that, in general, people perceived a decline in agricultural water availability and an increase in drought and flood events. The direct impacts of these changes were reduced crop yield, increased fallow lands, displacement of people from settlement areas, sedimentation of cultivable land and damage to properties. Household surveys showed that despite the perceived impacts on agriculture and livelihoods, only limited adaptation options are currently practised. Adaptation efforts are constrained by several factors, including: finance; technical knowledge; lack of awareness about adaptation options; lack of collective action; unclear property rights; and ineffective role of state agencies.

Opportunities and Challenges in the Trans-boundary Koshi River Basin

The Koshi river basin is shared between China, Nepal and India and is one of the key trans-boundary river basins in the Hindu-Kush Himalayas (HKH). The basin drains an area of about 88,000 km2 and is a river system with a high potential for investments in hydropower development as well as irrigation in the downstream areas. In addition the basin contains important ecosystems and protected areas which provide a range of biodiversity and related ecosystem services and sustain livelihoods. The basin is home to over 40 million people with agriculture as the dominant activity. However, the diverse topography, young geological formations, degree of glaciation and monsoon system make the basin particularly prone to water-related hazards like extreme flooding and landslides. Droughts are also experienced in the rain-fed tributaries of the basin during the dry season. Urbanisation and floodplain encroachment have also added pressures on the water bodies and ecosystems of the basin. Climate change will likely exacerbate these pressures with consequences for seasonal water availability, and food and energy security, highlighting the need for appropriate water management and disaster risk reduction strategies. A river basin approach, through the application of integrated water resources management (IWRM) principles, is essential to address the trans-boundary nature of many of these multifaceted issues. A conceptual framework for addressing these challenges within an integrated water and land resources management perspective for the Koshi basin is presented in this paper.

Landslides Inventory and Trans-boundary Risk Management in Koshi River Basin, Himalaya

Koshi River basin, which is a trans-boundary basin shared by China, Nepal and India, covers an area of about 87,500 km2. This study investigated the landslide locations in this basin by means of interpreting remote sensing images as well as field work. We could map 5653 landslides that are located within China and Nepal. Landslide caused different kinds of disasters including damage to public and private properties. The most common hazard pattern is supplying sources to debris flow, accounting for 48.38% of the number of landslides. The following patterns are soil erosion and blocking river, accounting for 25.18 and 18.98%, respectively. Cascading hazards related to landslides are very common in Koshi River basin. Three main cascading events were found there: landslide-dammed lake-outburst flood, GLOF-landslide and landslide-debris flow. These features make the disasters extend temporally and spatially. A framework for risk management in trans-boundary river basin was proposed to develop cooperation at academic and administrative levels among the involved countries.

Climate Change Adaptation, Water Infrastructure Development, and Responsive Governance in the Himalayas: The Case Study of Nepal’s Koshi River Basin

It is predicted that by the 2050s, the Koshi (Kosi) River basin, the largest Himalayan basin in Nepal, will be experiencing frequent and devastating flooding events and lower lean season flows due to climate change. This will threaten the livelihoods of millions of inhabitants. Development of water infrastructure has the potential to make water availability more consistent and secure. It could generate as much as 10,086 MW of economically feasible energy and irrigate approximately 500,000 ha of agricultural land. We argue that the challenges of water infrastructure development under climatic uncertainty can be overcome through systematic assessment of climatic and nonclimatic risks and responsive governance mechanisms that employ newer forms of stakeholder engagement and accountability, networks, partnerships and enhanced collaboration across sectors.